DIY Manual

31 | P a g e 10-543-1 REV A
DIY Manual
i. At rest means no charging (solar) or discharging (inverter)
ii. Best to wait 30 – 60 mins after last charge or discharge operation.
b. Batteries under charge will show a higher voltage than when at rest.
i. Batteries need higher voltage during charging to induce current to
flow into the batteries.
c. Batteries being discharged will show a lower voltage than when at rest.
2. Monitor Your Voltages
a. Assume your 12V system was designed for 50% daily DOD.
b. Develop a habit of checking your system voltage at same time every morning
and at night (before going to bed is perfect, as you will normally reduce loads
at this time).
c. Let’s say this morning the voltage reads 11.9V. 11.9V is below 12.1V (the
50% equivalent of half full), meaning too much power was consumed
overnight and the batteries are below 50% DOD.
i. Solution – Consume less power after the bank is fully charged OR
increase amp-hour capacity of your battery bank.
BATTERY CHARGING
Batteries charge in 3 stages:
1. Bulk – From 0% to about 75% SOC. Bulk is a varying voltage stage, constant current (or
as much current as the charge controller can produce).
2. Absorption – From about 75% to 95% SOC. During Absorb, the voltage is held constant
and the current slowly decreases to a point where the batteries are full and can take no
more current. This is called Ending Amps.
3. Float – 95% to 100%, Float maintains the batteries at 100% SOC.
Equalization (EQ) is a maintenance mode to reduce sulfates that attach to the battery’s lead
plates during charge and discharge cycles. The charge controller will hold a near constant
voltage during the EQ cycle, with varying current.
Obtain from your battery manufacturer a spec sheet that shows the correct charge voltages
for your battery model. You should also ask for their recommended ending amps, although
many manufacturers do not provide this figure. If not, use 1% - 3% of the overall bank’s
amp-hour capacity for ending amps.
Depleting flooded batteries below 50% will shorten their lifespan.